Photo-electric cell



Wom 25, 1 1,517,103

T. W. cAsE PHOTO ELECTRIC CELL Filed Anril 26. 4921 I WWW l/ L fi J 5 Q) wlllllll A 7 Patented New. 25, 1924.

ianata THEGDORE WllIQLARD CASE, F SCIPIO, NEW YORK, ASSIGNOB TO' CASE RESEARCH LABORATORY INCORPORATED, OF AUBURN, NEW YORK, A CORPORATION OF NEW YORK.

PHOTO-ELECTRIC CELL.

Application filed Aprifl 26, 1921. Serial No. 464,738. I

To all whom it may concern:

Be it known that I, THEODORE WILLARD CASE, of Scipio, in the county of Cayuga,

in the State of New York, have invented a greater effect upon thehuman eye-than others, or perhaps reversely, the human eye is more sensitive to certain colors than to others, and specifically, the human eye seems to be more sensitive to the yellow and green than to the red, blue and violet.

There has recently been developed a solution that permits the passage of light rays in proportion to the-color sensitivity of'the human eye, or the color effect of light rays upon the human eye. B the apparatus and process of my copending application, Serial No. 430,095, filed Dec. 11, 1920, I am able. to plot, or

produce a curve of light intensity, but said curve is dependent somewhat upon the character, or particular sensitivity of the light sensitive element used, and is, therefore, a curve. showing variations in the particular light sensitive element used as caused by variations in light intensity to which .it is exposed, for it 1s found that even light reactive materials are of greater sensitivity in some portions of the spectrum than in others. a Y It would be desirable to produce by my alpparatus what I term a luminosity curve, t at is, a'curve of light intensity which will indicate more clearly the efi'ect of the existing light upon the human eye, or the actual light as interpreted by thehuman eye v This result can be approximately accomplished in a preferred manner by utilizing a photo-electric .cell which itself interprets li ht as nearly like the human eyeas -possible combined with a. screen, or filter ma terial which permits passage of-light to the light sensitive material, orcell, in approximate proportion to its efiect upon the human eye.

My best information at this time is that a photo-electric cell in which the light sensitive elements consists of, or comprises ba-v rium, is best suited-for the purpose, as its and imused is hown' a" interpretation of light rays is more nearly like that of the human eye than any other practical material known to me.

This photo-electric cell may be formed in the manner described in my co-pending application Ser. No. 406,463, filed August 2.7,

screen, or filter, and I do not desire to limit myself to-the preferred combination of elements which I have discovered, except where specifically set forth in the appended claims;

It will be understood that the luminosity screen, or filter, may be formed separately from the vacuum bulb, and may be ap lied thereto, or confined or enclosed thereaibout in. any suitable manner so that ,the light." rays must pass through it before striking the light sensitive element.

However, at present, I prefer to form the vacuum bulb of the photo-electric cell it-'.

self of a glass material that itself constitutes a luminosity screen, or filter, and

through which the light rays must pass before striking the lightsensiti'vej element of the cell.

In the drawings Figure 1 illustrates an my-invention. Y

Figure 2 illustrates a somewhat embodiment of'myinventiom 1-.

Figure 3 illustrates. a further modified embodiment of my invention," 4' a a In the drawings in Figure 111 have dis,- 1 closed an ordinary photo-electric cell embodying a cathode -8 an anode and a; transparent bulb'15-, which in this'instance, is formed of glass of such embodiment of f rent f1 human eye. The bulb. -15 may be :formed ofany glassmat'erial that givesa age eye. lE or illustration, the bulb 'may' be made upof a combination of two glasses.

One of these glasses is a shade of yellow and the other a green. The yellow-glass Corning high transmischaracter as to permit passage of .light rays. t v

in proportion to the color sensitivity of the the battery voltage is compared ,at intervals a with the constant voltage of the standard cell v 3-, and the .rheostat -2,"is adjusted u1itil the proper currentis flowing. This is --4- which connects. the galvanometer f c llred in accordance with the disclosure 'of my.co-pen ding, application Se ial No. 406,463,;above referred to, and 'th'ephotosion ellow and is, for instance, about 42 one-t ousandths of an inch'in thickness,

while the green lass is Corning 401 BJ and may prefera ly'be about 66 one-thousandths of an inch in thickness. This 'de tailed specification is for illustrative purposes only.

I have illustrated the photo-electric cell of this invention as connected in the circuit of the 'po tentiometer galvanometer needle,

stands jmotipnless. This needle is the con,- trolling means of, the? recording apparatus. The potentiometer, is of the split-circuit, slide-wire' type. The=battery +1 which may consist of a few'dryl cells supplies continuously flowing current to the otentiometer circuit,the current being mamtained h constant by rheostat As the voltage in the battery -13. changes, tlm-current 111 Y the potentiometer circuit will also change.

To compensate for this change, a portionof accomplished bycompletingthe circuit at 5 in-series with the standard cell across the resistance coil 'Ifthe voltage across 'the coil is. not equalto the voltage. .of the jstandardcell, the galyanometer ,will

' deflect from its zero position in whichcase the rheostat -2 should be adjusted until the.

ga ano e r e i s z p tion. Thevoltages are now equal and opposite, tandthe roper current flowing.

A battery of suitableelectromotive force is connectedin circuit across the electrodes 8 and -9'.;of the photo-electric cell, which cell may, preferably, be manuelectric element as 8 should, preferably consist of or comprise barium.

. A variable resistance -10- is inserted in'the circuit between the-electrodes of the photo-electrieoell' so'that the'reiis a drop the circuit current flows through the'photo-electric cell in potential between the pointsu,11- and '12--- causing a flow. of current throu h thus formed. In addition't e i the contact -13 which contactis movjable with respect to the slideWire-14.-

T the current returning through the galvanometer 5 to'batte'ry Variations in eye.

thecurren't flowing in this circuit efi'ected b variations of resistance in the photoe ectric cell will cause deflection of the galvanometer needle, but'the needle will again the resistance may be used to account for suchvariations. The movement of the galvanometer effected by variations inthe current "-in the photo-electric cell circuit is utilized to control, the recordin mechanism. The operation of the Leeds & orthrup recorder is wellknown and need not be'here [further described,

In "thestructure illustrated, the bulb -15 is formed ,of glass of such a character as to-permit the passage of light rays injproportion to the c or sensitivity of the uman.eye, or approximately that proport1on.

\In Fi re 2 I have disclosed a photo-electric cell of similar construction, exceptthat the ordinary glass bulb -16- may be utilized and may be provided with a coating, layeror enclosure of material having the same, or substantially the samecharacteristics as the glass of the bulb of Figure'1.' This photorelectric cell, for illustrative purposes, is shown as connected in circuit with asource of potential -17 and a galvanometer --18-.

additional casing of somewhat lar rsize so as to form a chamber between t e bulb 18 of the photo-electric cell and the enclosing bulb, or casing 19 within which chamber a luminosity solution may be confined ii such a, manner that the rays of light must pass .therethrough before coming into contact with the sensitive element of the photo-electric cell.

It will be understood that the structures disclosed are merely illustrative of embodiments of my invention, which invention is capable of assuming various forms, the preferred embodiment-being as set forth, the combination of a hoto-electric cell including alight sensitive clement consisting of or comprising. barium, with a luminosity filter, that-i s,--a filter which permits the passageof light rays in approximate proportion to the color sensitively of the human However, my invention is much broader than. its present preferred embodiment, and the annexed cla ms are deemed to include any photo-electric cells that react to light mimics a luminosity filter that permits the passage of light rays to saidelement in approximate proportion to the efiect of said rays upon the human eye.

I claim:

1. A photo-electric cell in which the light sensitive element is provided witha' filter through which rays of light pass to reach the light sensitive element, said filter permitting the passage of light rays in proportion to the color sensitivity of the human eye. 2. A photo-electric cell in which a light sensitive element including barium is 'provided with a filter through which rays of .pass to reach the e light pass to reach thelight sensitive element, said filter being formed of a material WhlCll permits the passage of light rays in substantial accordance with the colorsensitivity of the human eye,

3. A photo-electric cell including alight sensitiveoelement and a bulb enclosing the 4 element, and through which rays of light ement, said bulb being formed of lass material which permits the passage of ight rays in substantial accordance with the color sensitivity of the human eye.

In witness whereof I have hereunto set my hand this 20th day of April, 1921.

THEODORE WILLARD CASE. Witnesses:

Buss S. OUSHMAN,

EAUL J. SroNABm'. 

